1. Field of the Invention
The present invention relates to a method of transferring mass with the aid of rotating surfaces. The invention also relates to apparatus for carrying out the method.
2. History of Related Art
It is known to improve the transfer of heat between a fluid and a surface, by disturbing the flow adjacent the surface, this being achieved in the case of so-called flat plate-type heat exchangers by corrugating the transfer surfaces or by providing these surfaces with turbulence-generating means.
Although this will disturb or agitate the flow of medium adjacent the surfaces, it does not induce the fluid to flow adjacent to or contiguously with the surfaces, which would improve heat transfer, but instead the fluid remains in a stationary layer close to the heat transfer surfaces, this layer having an insulating effect on the heat transfer process.
Another method of improving heat transfer is to allow the fluid to flow through narrow confined passageways, such as in the case of rotating heat-exchangers, wherein the short distance between the fluid and the wall is utilized in an endeavor to improve heat transfer. One drawback with this solution is that the major part of the fluid passes through the center of the passageway or channel, despite the narrowness of the passageway, and thus plays a smaller role in the heat transfer process. Another drawback is that the narrow passageways are liable to become blocked, and it is often necessary to take measures to prevent blocking of the passageways, therewith making the system more expensive. In the two cases described above, the measures taken to improve heat or mass transfer involve attempting to force into being an effect which is opposed to the intrinsic will of the fluid flow to flow in a certain manner.
U.S. Pat. No. 4,044,824 teaches a method of exchanging heat between two fluid flows which are conducted in heat-exchange relationship with one another in a rotating heat exchanger having fluid-accommodating bellows-like pockets. The differences in the density occurring between the fluid to be cooled and the fluid to be heated is utilized to create turbulent conditions that are intended to promote the exchange of heat and the transportation of the fluids. One drawback with this known arrangement, however, is that the entire fluid flow is passed through one and the same channel out of and into the bellows-like pockets, which limits the capacity of the heat-exchanger and impairs its ability to transfer heat, since the major part of the fluid flow passes through the center of the channel or passageway, as described above.
GB-A-936,059 teaches a heat-exchange method and a heat-exchanger which is comprised of an outer element, an inner element and an intermediate element of bellows-like form, these three elements defining therebetween two channels for the pass through of media between which an exchange of heat takes place. This method and the illustrated heat-exchanger have the drawbacks mentioned above with respect to the aforesaid U.S. patent.